diff --git a/core/datatrak.c b/core/datatrak.c
index f9f577c73..728efe5ab 100644
--- a/core/datatrak.c
+++ b/core/datatrak.c
@@ -356,7 +356,7 @@ static unsigned char *dt_dive_parser(unsigned char *runner, struct dive *dt_dive
 	 */
 	read_bytes(2);
 	if (tmp_2bytes != 0x7FFF && dt_dive->cylinders.nr > 0)
-		dt_dive->cylinders.cylinders[0].gas_used.mliter = lrint(dt_dive->cylinders.cylinders[0].type.size.mliter * (tmp_2bytes / 100.0));
+		get_cylinder(dt_dive, 0)->gas_used.mliter = lrint(get_cylinder(dt_dive, 0)->type.size.mliter * (tmp_2bytes / 100.0));
 
 	/*
 	 * Dive Type 1 -  Bit table. Subsurface don't have this record, but
@@ -532,10 +532,10 @@ static unsigned char *dt_dive_parser(unsigned char *runner, struct dive *dt_dive
 			goto bail;
 		}
 		if (is_nitrox && dt_dive->cylinders.nr > 0)
-			dt_dive->cylinders.cylinders[0].gasmix.o2.permille =
+			get_cylinder(dt_dive, 0)->gasmix.o2.permille =
 					lrint(membuf[23] & 0x0F ? 20.0 + 2 * (membuf[23] & 0x0F) : 21.0) * 10;
 		if (is_O2 && dt_dive->cylinders.nr > 0)
-			dt_dive->cylinders.cylinders[0].gasmix.o2.permille = membuf[23] * 10;
+			get_cylinder(dt_dive, 0)->gasmix.o2.permille = membuf[23] * 10;
 		free(compl_buffer);
 	}
 	JUMP(membuf, profile_length);
@@ -550,8 +550,8 @@ static unsigned char *dt_dive_parser(unsigned char *runner, struct dive *dt_dive
 	create_device_node(dt_dive->dc.model, dt_dive->dc.deviceid, "", "", dt_dive->dc.model);
 	dt_dive->dc.next = NULL;
 	if (!is_SCR && dt_dive->cylinders.nr > 0) {
-		dt_dive->cylinders.cylinders[0].end.mbar = dt_dive->cylinders.cylinders[0].start.mbar -
-			((dt_dive->cylinders.cylinders[0].gas_used.mliter / dt_dive->cylinders.cylinders[0].type.size.mliter) * 1000);
+		get_cylinder(dt_dive, 0)->end.mbar = get_cylinder(dt_dive, 0)->start.mbar -
+			((get_cylinder(dt_dive, 0)->gas_used.mliter / get_cylinder(dt_dive, 0)->type.size.mliter) * 1000);
 	}
 	free(devdata);
 	return membuf;
diff --git a/core/dive.c b/core/dive.c
index 7255416ac..20b39b6a3 100644
--- a/core/dive.c
+++ b/core/dive.c
@@ -264,7 +264,7 @@ struct gasmix get_gasmix_from_event(const struct dive *dive, const struct event
 	if (ev && event_is_gaschange(ev)) {
 		int index = ev->gas.index;
 		if (index >= 0 && index < dive->cylinders.nr)
-			return dive->cylinders.cylinders[index].gasmix;
+			return get_cylinder(dive, index)->gasmix;
 		return ev->gas.mix;
 	}
 	return dummy;
@@ -526,8 +526,8 @@ void copy_used_cylinders(const struct dive *s, struct dive *d, bool used_only)
 
 	clear_cylinder_table(&d->cylinders);
 	for (i = 0; i < s->cylinders.nr; i++) {
-		if (!used_only || is_cylinder_used(s, i) || s->cylinders.cylinders[i].cylinder_use == NOT_USED)
-			add_cloned_cylinder(&d->cylinders, s->cylinders.cylinders[i]);
+		if (!used_only || is_cylinder_used(s, i) || get_cylinder(s, i)->cylinder_use == NOT_USED)
+			add_cloned_cylinder(&d->cylinders, *get_cylinder(s, i));
 	}
 }
 
@@ -696,7 +696,7 @@ static int get_cylinder_used(const struct dive *dive, bool used[])
 	int i, num = 0;
 
 	for (i = 0; i < dive->cylinders.nr; i++) {
-		used[i] = cylinder_used(dive->cylinders.cylinders + i);
+		used[i] = cylinder_used(get_cylinder(dive, i));
 		if (used[i])
 			num++;
 	}
@@ -1000,8 +1000,8 @@ static void sanitize_cylinder_info(struct dive *dive)
 	int i;
 
 	for (i = 0; i < dive->cylinders.nr; i++) {
-		sanitize_gasmix(&dive->cylinders.cylinders[i].gasmix);
-		sanitize_cylinder_type(&dive->cylinders.cylinders[i].type);
+		sanitize_gasmix(&get_cylinder(dive, i)->gasmix);
+		sanitize_cylinder_type(&get_cylinder(dive, i)->type);
 	}
 }
 
@@ -1334,7 +1334,7 @@ static void simplify_dc_pressures(struct divecomputer *dc)
 static void fixup_start_pressure(struct dive *dive, int idx, pressure_t p)
 {
 	if (idx >= 0 && idx < dive->cylinders.nr) {
-		cylinder_t *cyl = dive->cylinders.cylinders + idx;
+		cylinder_t *cyl = get_cylinder(dive, idx);
 		if (p.mbar && !cyl->sample_start.mbar)
 			cyl->sample_start = p;
 	}
@@ -1343,7 +1343,7 @@ static void fixup_start_pressure(struct dive *dive, int idx, pressure_t p)
 static void fixup_end_pressure(struct dive *dive, int idx, pressure_t p)
 {
 	if (idx >= 0 && idx < dive->cylinders.nr) {
-		cylinder_t *cyl = dive->cylinders.cylinders + idx;
+		cylinder_t *cyl = get_cylinder(dive, idx);
 		if (p.mbar && !cyl->sample_end.mbar)
 			cyl->sample_end = p;
 	}
@@ -1415,7 +1415,7 @@ static bool validate_gaschange(struct dive *dive, struct event *event)
 
 	/* Fix up the event to have the right information */
 	event->gas.index = index;
-	event->gas.mix = dive->cylinders.cylinders[index].gasmix;
+	event->gas.mix = get_cylinder(dive, index)->gasmix;
 
 	/* Convert to odd libdivecomputer format */
 	o2 = get_o2(event->gas.mix);
@@ -1540,7 +1540,7 @@ struct dive *fixup_dive(struct dive *dive)
 	fixup_watertemp(dive);
 	fixup_airtemp(dive);
 	for (i = 0; i < dive->cylinders.nr; i++) {
-		cylinder_t *cyl = dive->cylinders.cylinders + i;
+		cylinder_t *cyl = get_cylinder(dive, i);
 		add_cylinder_description(&cyl->type);
 		if (same_rounded_pressure(cyl->sample_start, cyl->start))
 			cyl->start.mbar = 0;
@@ -1923,7 +1923,7 @@ extern int get_cylinder_idx_by_use(const struct dive *dive, enum cylinderuse cyl
 {
 	int cylinder_index;
 	for (cylinder_index = 0; cylinder_index < dive->cylinders.nr; cylinder_index++) {
-		if (dive->cylinders.cylinders[cylinder_index].cylinder_use == cylinder_use_type)
+		if (get_cylinder(dive, cylinder_index)->cylinder_use == cylinder_use_type)
 			return cylinder_index; // return the index of the cylinder with that cylinder use type
 	}
 	return -1; // negative number means cylinder_use_type not found in list of cylinders
@@ -2073,7 +2073,7 @@ int same_gasmix_cylinder(const cylinder_t *cyl, int cylid, const struct dive *di
 	for (int i = 0; i < dive->cylinders.nr; i++) {
 		if (i == cylid)
 			continue;
-		struct gasmix gas2 = dive->cylinders.cylinders[i].gasmix;
+		struct gasmix gas2 = get_cylinder(dive, i)->gasmix;
 		if (gasmix_distance(mygas, gas2) == 0 && (is_cylinder_used(dive, i) || check_unused))
 			return i;
 	}
@@ -2108,7 +2108,7 @@ static int match_cylinder(const cylinder_t *cyl, const struct dive *dive, const
 
 		if (!used[i])
 			continue;
-		target = dive->cylinders.cylinders + i;
+		target = get_cylinder(dive, i);
 		if (!same_gasmix(cyl->gasmix, target->gasmix))
 			continue;
 		if (cyl->cylinder_use != target->cylinder_use)
@@ -2197,7 +2197,7 @@ static void merge_cylinders(struct dive *res, const struct dive *a, const struct
 		if (!used_in_b[i])
 			continue;
 
-		j = match_cylinder(b->cylinders.cylinders + i, a, used_in_a);
+		j = match_cylinder(get_cylinder(b, i), a, used_in_a);
 		if (j < 0)
 			continue;
 
@@ -2216,14 +2216,14 @@ static void merge_cylinders(struct dive *res, const struct dive *a, const struct
 		mapping_a[j] = res->cylinders.nr;
 		used_in_a[i] = false;
 		used_in_b[j] = false;
-		merge_one_cylinder(&res->cylinders, a->cylinders.cylinders + j, b->cylinders.cylinders + i);
+		merge_one_cylinder(&res->cylinders, get_cylinder(a, j), get_cylinder(b, i));
 	}
 
 	/* Now copy all the used cylinders from 'a' that are used but have not been matched */
 	for (i = 0; i < a->cylinders.nr; i++) {
 		if (used_in_a[i]) {
 			mapping_a[i] = res->weightsystems.nr;
-			add_cloned_cylinder(&res->cylinders, a->cylinders.cylinders[i]);
+			add_cloned_cylinder(&res->cylinders, *get_cylinder(a, i));
 		}
 	}
 
@@ -2231,7 +2231,7 @@ static void merge_cylinders(struct dive *res, const struct dive *a, const struct
 	for (i = 0; i < b->cylinders.nr; i++) {
 		if (used_in_b[i]) {
 			mapping_b[i] = res->weightsystems.nr;
-			add_cloned_cylinder(&res->cylinders, b->cylinders.cylinders[i]);
+			add_cloned_cylinder(&res->cylinders, *get_cylinder(b, i));
 		}
 	}
 
@@ -3018,10 +3018,11 @@ static void force_fixup_dive(struct dive *d)
 	d->maxtemp.mkelvin = 0;
 	d->mintemp.mkelvin = 0;
 	for (int i = 0; i < d->cylinders.nr; i++) {
-		old_pressures[i].start = d->cylinders.cylinders[i].start;
-		old_pressures[i].end = d->cylinders.cylinders[i].end;
-		d->cylinders.cylinders[i].start.mbar = 0;
-		d->cylinders.cylinders[i].end.mbar = 0;
+		cylinder_t *cyl = get_cylinder(d, i);
+		old_pressures[i].start = cyl->start;
+		old_pressures[i].end = cyl->end;
+		cyl->start.mbar = 0;
+		cyl->end.mbar = 0;
 	}
 
 	fixup_dive(d);
@@ -3041,10 +3042,10 @@ static void force_fixup_dive(struct dive *d)
 	if (!d->duration.seconds)
 		d->duration = old_duration;
 	for (int i = 0; i < d->cylinders.nr; i++) {
-		if (!d->cylinders.cylinders[i].start.mbar)
-			d->cylinders.cylinders[i].start = old_pressures[i].start;
-		if (!d->cylinders.cylinders[i].end.mbar)
-			d->cylinders.cylinders[i].end = old_pressures[i].end;
+		if (!get_cylinder(d, i)->start.mbar)
+			get_cylinder(d, i)->start = old_pressures[i].start;
+		if (!get_cylinder(d, i)->end.mbar)
+			get_cylinder(d, i)->end = old_pressures[i].end;
 	}
 	free(old_pressures);
 }
@@ -4009,7 +4010,7 @@ struct gasmix get_gasmix(const struct dive *dive, const struct divecomputer *dc,
 	if (!ev) {
 		/* on first invocation, get initial gas mix and first event (if any) */
 		int cyl = explicit_first_cylinder(dive, dc);
-		res = dive->cylinders.cylinders[cyl].gasmix;
+		res = get_cylinder(dive, cyl)->gasmix;
 		ev = dc ? get_next_event(dc->events, "gaschange") : NULL;
 	} else {
 		res = gasmix;
diff --git a/core/divelist.c b/core/divelist.c
index 5eae5e638..451ed70a7 100644
--- a/core/divelist.c
+++ b/core/divelist.c
@@ -66,7 +66,7 @@ void get_dive_gas(const struct dive *dive, int *o2_p, int *he_p, int *o2max_p)
 
 
 	for (i = 0; i < dive->cylinders.nr; i++) {
-		const cylinder_t *cyl = dive->cylinders.cylinders + i;
+		const cylinder_t *cyl = get_cylinder(dive, i);
 		int o2 = get_o2(cyl->gasmix);
 		int he = get_he(cyl->gasmix);
 
@@ -349,7 +349,7 @@ static double calculate_airuse(const struct dive *dive)
 
 	for (i = 0; i < dive->cylinders.nr; i++) {
 		pressure_t start, end;
-		const cylinder_t *cyl = dive->cylinders.cylinders + i;
+		const cylinder_t *cyl = get_cylinder(dive, i);
 
 		start = cyl->start.mbar ? cyl->start : cyl->sample_start;
 		end = cyl->end.mbar ? cyl->end : cyl->sample_end;
diff --git a/core/equipment.c b/core/equipment.c
index 3a2e6db4b..39505a39d 100644
--- a/core/equipment.c
+++ b/core/equipment.c
@@ -279,7 +279,7 @@ void reset_cylinders(struct dive *dive, bool track_gas)
 	pressure_t decopo2 = {.mbar = prefs.decopo2};
 
 	for (int i = 0; i < dive->cylinders.nr; i++) {
-		cylinder_t *cyl = &dive->cylinders.cylinders[i];
+		cylinder_t *cyl = get_cylinder(dive, i);
 		if (cyl->depth.mm == 0) /* if the gas doesn't give a mod, calculate based on prefs */
 			cyl->depth = gas_mod(cyl->gasmix, decopo2, dive, M_OR_FT(3,10));
 		if (track_gas)
@@ -308,10 +308,10 @@ void copy_cylinder_types(const struct dive *s, struct dive *d)
 		return;
 
 	for (i = 0; i < s->cylinders.nr && i < d->cylinders.nr; i++)
-		copy_cylinder_type(s->cylinders.cylinders + i, d->cylinders.cylinders + i);
+		copy_cylinder_type(get_cylinder(s, i), get_cylinder(d, i));
 
 	for ( ; i < s->cylinders.nr; i++)
-		add_cloned_cylinder(&d->cylinders, s->cylinders.cylinders[i]);
+		add_cloned_cylinder(&d->cylinders, *get_cylinder(s, i));
 }
 
 cylinder_t *add_empty_cylinder(struct cylinder_table *t)
@@ -355,7 +355,7 @@ void dump_cylinders(struct dive *dive, bool verbose)
 {
 	printf("Cylinder list:\n");
 	for (int i = 0; i < dive->cylinders; i++) {
-		cylinder_t *cyl = &dive->cylinders.cylinders[i];
+		cylinder_t *cyl = get_cylinder(dive, i);
 
 		printf("%02d: Type     %s, %3.1fl, %3.0fbar\n", i, cyl->type.description, cyl->type.size.mliter / 1000.0, cyl->type.workingpressure.mbar / 1000.0);
 		printf("    Gasmix   O2 %2.0f%% He %2.0f%%\n", cyl->gasmix.o2.permille / 10.0, cyl->gasmix.he.permille / 10.0);
diff --git a/core/gaspressures.c b/core/gaspressures.c
index a69dbb295..bf329add4 100644
--- a/core/gaspressures.c
+++ b/core/gaspressures.c
@@ -238,7 +238,7 @@ static void fill_missing_tank_pressures(struct dive *dive, struct plot_info *pi,
 	if (!track_pr)
 		return;
 
-	if (dive->cylinders.cylinders[cyl].cylinder_use == OC_GAS)
+	if (get_cylinder(dive, cyl)->cylinder_use == OC_GAS)
 		strategy = SAC;
 	else
 		strategy = TIME;
@@ -302,7 +302,7 @@ static void fill_missing_tank_pressures(struct dive *dive, struct plot_info *pi,
 			last_segment = segment;
 		}
 
-		if(dive->cylinders.cylinders[cyl].cylinder_use == OC_GAS) {
+		if(get_cylinder(dive, cyl)->cylinder_use == OC_GAS) {
 
 			/* if this segment has pressure_time, then calculate a new interpolated pressure */
 			if (interpolate.pressure_time) {
@@ -366,7 +366,7 @@ void populate_pressure_information(struct dive *dive, struct divecomputer *dc, s
 {
 	UNUSED(dc);
 	int first, last, cyl;
-	cylinder_t *cylinder = dive->cylinders.cylinders + sensor;
+	cylinder_t *cylinder = get_cylinder(dive, sensor);
 	pr_track_t *track = NULL;
 	pr_track_t *current = NULL;
 	const struct event *ev, *b_ev;
diff --git a/core/import-divinglog.c b/core/import-divinglog.c
index 5b9e4be3b..f3a62eaff 100644
--- a/core/import-divinglog.c
+++ b/core/import-divinglog.c
@@ -130,7 +130,7 @@ static int divinglog_profile(void *param, int columns, char **data, char **colum
 			state->cur_sample->pressure[0].mbar = pressure * 100;
 			state->cur_sample->rbt.seconds = rbt;
 			if (oldcyl != tank && tank >= 0 && tank < state->cur_dive->cylinders.nr) {
-				struct gasmix mix = state->cur_dive->cylinders.cylinders[tank].gasmix;
+				struct gasmix mix = get_cylinder(state->cur_dive, tank)->gasmix;
 				int o2 = get_o2(mix);
 				int he = get_he(mix);
 
diff --git a/core/import-shearwater.c b/core/import-shearwater.c
index 1c1e68eb4..3cedb3f22 100644
--- a/core/import-shearwater.c
+++ b/core/import-shearwater.c
@@ -61,7 +61,7 @@ static int shearwater_changes(void *param, int columns, char **data, char **colu
 	int i;
 	bool found = false;
 	for (i = 0; i < state->cur_dive->cylinders.nr; ++i) {
-		const cylinder_t *cyl = &state->cur_dive->cylinders.cylinders[i];
+		const cylinder_t *cyl = get_cylinder(state->cur_dive, i);
 		if (cyl->gasmix.o2.permille == o2 && cyl->gasmix.he.permille == he) {
 			found = true;
 			break;
diff --git a/core/parse-xml.c b/core/parse-xml.c
index 0f297bf9a..bca0269a3 100644
--- a/core/parse-xml.c
+++ b/core/parse-xml.c
@@ -704,7 +704,7 @@ void add_gas_switch_event(struct dive *dive, struct divecomputer *dc, int second
 		return;
 	}
 	/* The gas switch event format is insane for historical reasons */
-	struct gasmix mix = dive->cylinders.cylinders[idx].gasmix;
+	struct gasmix mix = get_cylinder(dive, idx)->gasmix;
 	int o2 = get_o2(mix);
 	int he = get_he(mix);
 	struct event *ev;
@@ -1242,7 +1242,7 @@ static void gps_picture_location(char *buffer, struct picture *pic)
 static void try_to_fill_dive(struct dive *dive, const char *name, char *buf, struct parser_state *state)
 {
 	char *hash = NULL;
-	cylinder_t *cyl = dive->cylinders.nr > 0 ? &dive->cylinders.cylinders[dive->cylinders.nr - 1] : NULL;
+	cylinder_t *cyl = dive->cylinders.nr > 0 ? get_cylinder(dive, dive->cylinders.nr - 1) : NULL;
 	pressure_t p;
 	start_match("dive", name, buf);
 
@@ -1904,7 +1904,7 @@ int parse_dlf_buffer(unsigned char *buffer, size_t size, struct dive_table *tabl
 
 				found = false;
 				for (i = 0; i < state.cur_dive->cylinders.nr; ++i) {
-					const cylinder_t *cyl = &state.cur_dive->cylinders.cylinders[i];
+					const cylinder_t *cyl = get_cylinder(state.cur_dive, i);
 					if (cyl->gasmix.o2.permille == ptr[6] * 10 && cyl->gasmix.he.permille == ptr[7] * 10) {
 						found = true;
 						break;
diff --git a/core/planner.c b/core/planner.c
index 4a480640d..51453e1ee 100644
--- a/core/planner.c
+++ b/core/planner.c
@@ -409,7 +409,7 @@ static struct gaschanges *analyze_gaslist(struct diveplan *diveplan, struct dive
 	int nr = 0;
 	struct gaschanges *gaschanges = NULL;
 	struct divedatapoint *dp = diveplan->dp;
-	int best_depth = dive->cylinders.cylinders[*asc_cylinder].depth.mm;
+	int best_depth = get_cylinder(dive, *asc_cylinder)->depth.mm;
 	bool total_time_zero = true;
 	while (dp) {
 		if (dp->time == 0 && total_time_zero) {
@@ -444,7 +444,7 @@ static struct gaschanges *analyze_gaslist(struct diveplan *diveplan, struct dive
 	for (nr = 0; nr < *gaschangenr; nr++) {
 		int idx = gaschanges[nr].gasidx;
 		printf("gaschange nr %d: @ %5.2lfm gasidx %d (%s)\n", nr, gaschanges[nr].depth / 1000.0,
-		       idx, gasname(dive->cylinders.cylinders[idx].gasmix));
+		       idx, gasname(&get_cylinder(&dive, idx)->gasmix));
 	}
 #endif
 	return gaschanges;
@@ -527,7 +527,7 @@ int ascent_velocity(int depth, int avg_depth, int bottom_time)
 
 static void track_ascent_gas(int depth, struct dive *dive, int cylinder_id, int avg_depth, int bottom_time, bool safety_stop, enum divemode_t divemode)
 {
-	cylinder_t *cylinder = &dive->cylinders.cylinders[cylinder_id];
+	cylinder_t *cylinder = get_cylinder(dive, cylinder_id);
 	while (depth > 0) {
 		int deltad = ascent_velocity(depth, avg_depth, bottom_time) * TIMESTEP;
 		if (deltad > depth)
@@ -598,7 +598,7 @@ static bool enough_gas(const struct dive *dive, int current_cylinder)
 	cylinder_t *cyl;
 	if (current_cylinder < 0 || current_cylinder >= dive->cylinders.nr)
 		return false;
-	cyl = &dive->cylinders.cylinders[current_cylinder];
+	cyl = get_cylinder(dive, current_cylinder);
 
 	if (!cyl->start.mbar)
 		return true;
@@ -732,7 +732,7 @@ bool plan(struct deco_state *ds, struct diveplan *diveplan, struct dive *dive, i
 	const struct event *ev = NULL;
 	divemode = UNDEF_COMP_TYPE;
 	divemode = get_current_divemode(&dive->dc, bottom_time, &ev, &divemode);
-	gas = dive->cylinders.cylinders[current_cylinder].gasmix;
+	gas = get_cylinder(dive, current_cylinder)->gasmix;
 
 	po2 = sample->setpoint.mbar;
 	depth = dive->dc.sample[dive->dc.samples - 1].depth.mm;
@@ -787,11 +787,11 @@ bool plan(struct deco_state *ds, struct diveplan *diveplan, struct dive *dive, i
 		// How long can we stay at the current depth and still directly ascent to the surface?
 		do {
 			add_segment(ds, depth_to_bar(depth, dive),
-				    dive->cylinders.cylinders[current_cylinder].gasmix,
+				    get_cylinder(dive, current_cylinder)->gasmix,
 				    timestep, po2, divemode, prefs.bottomsac);
-			update_cylinder_pressure(dive, depth, depth, timestep, prefs.bottomsac, &dive->cylinders.cylinders[current_cylinder], false, divemode);
+			update_cylinder_pressure(dive, depth, depth, timestep, prefs.bottomsac, get_cylinder(dive, current_cylinder), false, divemode);
 			clock += timestep;
-		} while (trial_ascent(ds, 0, depth, 0, avg_depth, bottom_time, dive->cylinders.cylinders[current_cylinder].gasmix,
+		} while (trial_ascent(ds, 0, depth, 0, avg_depth, bottom_time, get_cylinder(dive, current_cylinder)->gasmix,
 				      po2, diveplan->surface_pressure / 1000.0, dive, divemode) &&
 			 enough_gas(dive, current_cylinder) && clock < 6 * 3600);
 
@@ -799,7 +799,7 @@ bool plan(struct deco_state *ds, struct diveplan *diveplan, struct dive *dive, i
 		// In the best of all worlds, we would roll back also the last add_segment in terms of caching deco state, but
 		// let's ignore that since for the eventual ascent in recreational mode, nobody looks at the ceiling anymore,
 		// so we don't really have to compute the deco state.
-		update_cylinder_pressure(dive, depth, depth, -timestep, prefs.bottomsac, &dive->cylinders.cylinders[current_cylinder], false, divemode);
+		update_cylinder_pressure(dive, depth, depth, -timestep, prefs.bottomsac, get_cylinder(dive, current_cylinder), false, divemode);
 		clock -= timestep;
 		plan_add_segment(diveplan, clock - previous_point_time, depth, current_cylinder, po2, true, divemode);
 		previous_point_time = clock;
@@ -837,7 +837,7 @@ bool plan(struct deco_state *ds, struct diveplan *diveplan, struct dive *dive, i
 
 	if (best_first_ascend_cylinder != current_cylinder) {
 		current_cylinder = best_first_ascend_cylinder;
-		gas = dive->cylinders.cylinders[current_cylinder].gasmix;
+		gas = get_cylinder(dive, current_cylinder)->gasmix;
 
 #if DEBUG_PLAN & 16
 		printf("switch to gas %d (%d/%d) @ %5.2lfm\n", best_first_ascend_cylinder,
@@ -851,7 +851,7 @@ bool plan(struct deco_state *ds, struct diveplan *diveplan, struct dive *dive, i
 		divemode = OC;
 		po2 = 0;
 		add_segment(ds, depth_to_bar(depth, dive),
-			dive->cylinders.cylinders[current_cylinder].gasmix,
+			get_cylinder(dive, current_cylinder)->gasmix,
 			prefs.min_switch_duration, po2, divemode, prefs.bottomsac);
 		plan_add_segment(diveplan, prefs.min_switch_duration, depth, current_cylinder, po2, false, divemode);
 		clock += prefs.min_switch_duration;
@@ -893,7 +893,7 @@ bool plan(struct deco_state *ds, struct diveplan *diveplan, struct dive *dive, i
 		last_ascend_rate = ascent_velocity(depth, avg_depth, bottom_time);
 		/* Always prefer the best_first_ascend_cylinder if it has the right gasmix.
 		 * Otherwise take first cylinder from list with rightgasmix  */
-		if (same_gasmix(gas, dive->cylinders.cylinders[best_first_ascend_cylinder].gasmix))
+		if (same_gasmix(gas, get_cylinder(dive, best_first_ascend_cylinder)->gasmix))
 			current_cylinder = best_first_ascend_cylinder;
 		else
 			current_cylinder = get_gasidx(dive, gas);
@@ -918,7 +918,7 @@ bool plan(struct deco_state *ds, struct diveplan *diveplan, struct dive *dive, i
 					deltad = depth - stoplevels[stopidx];
 
 				add_segment(ds, depth_to_bar(depth, dive),
-								dive->cylinders.cylinders[current_cylinder].gasmix,
+								get_cylinder(dive, current_cylinder)->gasmix,
 								TIMESTEP, po2, divemode, prefs.decosac);
 				last_segment_min_switch = false;
 				clock += TIMESTEP;
@@ -943,21 +943,21 @@ bool plan(struct deco_state *ds, struct diveplan *diveplan, struct dive *dive, i
 				if (current_cylinder != gaschanges[gi].gasidx) {
 					if (!prefs.switch_at_req_stop ||
 							!trial_ascent(ds, 0, depth, stoplevels[stopidx - 1], avg_depth, bottom_time,
-							dive->cylinders.cylinders[current_cylinder].gasmix, po2, diveplan->surface_pressure / 1000.0, dive, divemode) || get_o2(dive->cylinders.cylinders[current_cylinder].gasmix) < 160) {
+							get_cylinder(dive, current_cylinder)->gasmix, po2, diveplan->surface_pressure / 1000.0, dive, divemode) || get_o2(get_cylinder(dive, current_cylinder)->gasmix) < 160) {
 						if (is_final_plan)
 							plan_add_segment(diveplan, clock - previous_point_time, depth, current_cylinder, po2, false, divemode);
 						stopping = true;
 						previous_point_time = clock;
 						current_cylinder = gaschanges[gi].gasidx;
-						gas = dive->cylinders.cylinders[current_cylinder].gasmix;
+						gas = get_cylinder(dive, current_cylinder)->gasmix;
 #if DEBUG_PLAN & 16
 						printf("switch to gas %d (%d/%d) @ %5.2lfm\n", gaschanges[gi].gasidx,
 							(get_o2(&gas) + 5) / 10, (get_he(&gas) + 5) / 10, gaschanges[gi].depth / 1000.0);
 #endif
 						/* Stop for the minimum duration to switch gas unless we switch to o2 */
-						if (!last_segment_min_switch && get_o2(dive->cylinders.cylinders[current_cylinder].gasmix) != 1000) {
+						if (!last_segment_min_switch && get_o2(get_cylinder(dive, current_cylinder)->gasmix) != 1000) {
 							add_segment(ds, depth_to_bar(depth, dive),
-								dive->cylinders.cylinders[current_cylinder].gasmix,
+								get_cylinder(dive, current_cylinder)->gasmix,
 								prefs.min_switch_duration, po2, divemode, prefs.decosac);
 							clock += prefs.min_switch_duration;
 							last_segment_min_switch = true;
@@ -977,7 +977,7 @@ bool plan(struct deco_state *ds, struct diveplan *diveplan, struct dive *dive, i
 			while (1) {
 				/* Check if ascending to next stop is clear, go back and wait if we hit the ceiling on the way */
 				if (trial_ascent(ds, 0, depth, stoplevels[stopidx], avg_depth, bottom_time,
-						dive->cylinders.cylinders[current_cylinder].gasmix, po2, diveplan->surface_pressure / 1000.0, dive, divemode)) {
+						get_cylinder(dive, current_cylinder)->gasmix, po2, diveplan->surface_pressure / 1000.0, dive, divemode)) {
 					decostoptable[decostopcounter].depth = depth;
 					decostoptable[decostopcounter].time = 0;
 					decostopcounter++;
@@ -1003,15 +1003,15 @@ bool plan(struct deco_state *ds, struct diveplan *diveplan, struct dive *dive, i
 				 */
 				if (pendinggaschange) {
 					current_cylinder = gaschanges[gi + 1].gasidx;
-					gas = dive->cylinders.cylinders[current_cylinder].gasmix;
+					gas = get_cylinder(dive, current_cylinder)->gasmix;
 #if DEBUG_PLAN & 16
 					printf("switch to gas %d (%d/%d) @ %5.2lfm\n", gaschanges[gi + 1].gasidx,
 						(get_o2(&gas) + 5) / 10, (get_he(&gas) + 5) / 10, gaschanges[gi + 1].depth / 1000.0);
 #endif
 					/* Stop for the minimum duration to switch gas unless we switch to o2 */
-					if (!last_segment_min_switch && get_o2(dive->cylinders.cylinders[current_cylinder].gasmix) != 1000) {
+					if (!last_segment_min_switch && get_o2(get_cylinder(dive, current_cylinder)->gasmix) != 1000) {
 						add_segment(ds, depth_to_bar(depth, dive),
-							dive->cylinders.cylinders[current_cylinder].gasmix,
+							get_cylinder(dive, current_cylinder)->gasmix,
 							prefs.min_switch_duration, po2, divemode, prefs.decosac);
 						clock += prefs.min_switch_duration;
 						last_segment_min_switch = true;
@@ -1020,7 +1020,7 @@ bool plan(struct deco_state *ds, struct diveplan *diveplan, struct dive *dive, i
 				}
 
 				int new_clock = wait_until(ds, dive, clock, clock, laststoptime * 2 + 1, timestep, depth, stoplevels[stopidx], avg_depth,
-					bottom_time, dive->cylinders.cylinders[current_cylinder].gasmix, po2, diveplan->surface_pressure / 1000.0, divemode);
+					bottom_time, get_cylinder(dive, current_cylinder)->gasmix, po2, diveplan->surface_pressure / 1000.0, divemode);
 				laststoptime = new_clock - clock;
 				/* Finish infinite deco */
 				if (laststoptime >= 48 * 3600 && depth >= 6000) {
@@ -1035,12 +1035,12 @@ bool plan(struct deco_state *ds, struct diveplan *diveplan, struct dive *dive, i
 					 * backgas.  This could be customized if there were demand.
 					 */
 					if (break_cylinder == -1) {
-						if (get_o2(dive->cylinders.cylinders[best_first_ascend_cylinder].gasmix) <= 320)
+						if (get_o2(get_cylinder(dive, best_first_ascend_cylinder)->gasmix) <= 320)
 							break_cylinder = best_first_ascend_cylinder;
 						else
 							break_cylinder = 0;
 					}
-					if (get_o2(dive->cylinders.cylinders[current_cylinder].gasmix) == 1000) {
+					if (get_o2(get_cylinder(dive, current_cylinder)->gasmix) == 1000) {
 						if (laststoptime >= 12 * 60) {
 							laststoptime = 12 * 60;
 							new_clock = clock + laststoptime;
@@ -1051,7 +1051,7 @@ bool plan(struct deco_state *ds, struct diveplan *diveplan, struct dive *dive, i
 								plan_add_segment(diveplan, laststoptime, depth, current_cylinder, po2, false, divemode);
 							previous_point_time = clock + laststoptime;
 							current_cylinder = break_cylinder;
-							gas = dive->cylinders.cylinders[current_cylinder].gasmix;
+							gas = get_cylinder(dive, current_cylinder)->gasmix;
 						}
 					} else if (o2break_next) {
 						if (laststoptime >= 6 * 60) {
@@ -1063,11 +1063,11 @@ bool plan(struct deco_state *ds, struct diveplan *diveplan, struct dive *dive, i
 								plan_add_segment(diveplan, laststoptime, depth, current_cylinder, po2, false, divemode);
 							previous_point_time = clock + laststoptime;
 							current_cylinder = breakfrom_cylinder;
-							gas = dive->cylinders.cylinders[current_cylinder].gasmix;
+							gas = get_cylinder(dive, current_cylinder)->gasmix;
 						}
 					}
 				}
-				add_segment(ds, depth_to_bar(depth, dive), dive->cylinders.cylinders[stop_cylinder].gasmix,
+				add_segment(ds, depth_to_bar(depth, dive), get_cylinder(dive, stop_cylinder)->gasmix,
 					    laststoptime, po2, divemode, prefs.decosac);
 				last_segment_min_switch = false;
 				decostoptable[decostopcounter].depth = depth;
diff --git a/core/plannernotes.c b/core/plannernotes.c
index dd909108a..6b3095082 100644
--- a/core/plannernotes.c
+++ b/core/plannernotes.c
@@ -190,13 +190,13 @@ void add_plan_to_notes(struct diveplan *diveplan, struct dive *dive, bool show_d
 		nextdp = dp->next;
 		if (dp->time == 0)
 			continue;
-		gasmix = dive->cylinders.cylinders[dp->cylinderid].gasmix;
+		gasmix = get_cylinder(dive, dp->cylinderid)->gasmix;
 		depthvalue = get_depth_units(dp->depth.mm, &decimals, &depth_unit);
 		/* analyze the dive points ahead */
 		while (nextdp && nextdp->time == 0)
 			nextdp = nextdp->next;
 		if (nextdp)
-			newgasmix = dive->cylinders.cylinders[nextdp->cylinderid].gasmix;
+			newgasmix = get_cylinder(dive, nextdp->cylinderid)->gasmix;
 		gaschange_after = (nextdp && (gasmix_distance(gasmix, newgasmix)));
 		gaschange_before =  (gasmix_distance(lastprintgasmix, gasmix));
 		rebreatherchange_after = (nextdp && (dp->setpoint != nextdp->setpoint || dp->divemode != nextdp->divemode));
@@ -466,7 +466,7 @@ void add_plan_to_notes(struct diveplan *diveplan, struct dive *dive, bool show_d
 		const char *unit, *pressure_unit, *depth_unit;
 		char warning[1000] = "";
 		char mingas[1000] = "";
-		cylinder_t *cyl = &dive->cylinders.cylinders[gasidx];
+		cylinder_t *cyl = get_cylinder(dive, gasidx);
 		if (cyl->cylinder_use == NOT_USED)
 			continue;
 
@@ -581,7 +581,7 @@ void add_plan_to_notes(struct diveplan *diveplan, struct dive *dive, bool show_d
 		while (dp) {
 			if (dp->time != 0) {
 				struct gas_pressures pressures;
-				struct gasmix gasmix = dive->cylinders.cylinders[dp->cylinderid].gasmix;
+				struct gasmix gasmix = get_cylinder(dive, dp->cylinderid)->gasmix;
 
 				current_divemode = get_current_divemode(&dive->dc, dp->time, &evd, &current_divemode);
 				amb = depth_to_atm(dp->depth.mm, dive);
diff --git a/core/profile.c b/core/profile.c
index 4d35155b2..bee2b7a4a 100644
--- a/core/profile.c
+++ b/core/profile.c
@@ -189,7 +189,7 @@ static int get_local_sac(struct plot_info *pi, int idx1, int idx2, struct dive *
 	depth = (entry1->depth + entry2->depth) / 2;
 	atm = depth_to_atm(depth, dive);
 
-	cyl = dive->cylinders.cylinders + index;
+	cyl = get_cylinder(dive, index);
 
 	airuse = gas_volume(cyl, a) - gas_volume(cyl, b);
 
@@ -414,7 +414,7 @@ static void calculate_max_limits_new(struct dive *dive, struct divecomputer *giv
 
 	/* Get the per-cylinder maximum pressure if they are manual */
 	for (cyl = 0; cyl < dive->cylinders.nr; cyl++) {
-		int mbar = dive->cylinders.cylinders[cyl].start.mbar;
+		int mbar = get_cylinder(dive, cyl)->start.mbar;
 		if (mbar > maxpressure)
 			maxpressure = mbar;
 		if (mbar < minpressure)
@@ -677,7 +677,7 @@ static int sac_between(struct dive *dive, struct plot_info *pi, int first, int l
 
 		a.mbar = get_plot_pressure(pi, first, i);
 		b.mbar = get_plot_pressure(pi, last, i);
-		cyl = dive->cylinders.cylinders + i;
+		cyl = get_cylinder(dive, i);
 		cyluse = gas_volume(cyl, a) - gas_volume(cyl, b);
 		if (cyluse > 0)
 			airuse += cyluse;
@@ -800,7 +800,7 @@ static void matching_gases(struct dive *dive, struct gasmix gasmix, bool gases[]
 	int i;
 
 	for (i = 0; i < dive->cylinders.nr; i++)
-		gases[i] = same_gasmix(gasmix, dive->cylinders.cylinders[i].gasmix);
+		gases[i] = same_gasmix(gasmix, get_cylinder(dive, i)->gasmix);
 }
 
 static void calculate_sac(struct dive *dive, struct divecomputer *dc, struct plot_info *pi)
@@ -890,7 +890,7 @@ static void setup_gas_sensor_pressure(const struct dive *dive, const struct dive
 	// Fill in "seen[]" array - mark cylinders we're not interested
 	// in as negative.
 	for (i = 0; i < pi->nr_cylinders; i++) {
-		const cylinder_t *cyl = dive->cylinders.cylinders + i;
+		const cylinder_t *cyl = get_cylinder(dive, i);
 		int start = cyl->start.mbar;
 		int end = cyl->end.mbar;
 
@@ -920,7 +920,7 @@ static void setup_gas_sensor_pressure(const struct dive *dive, const struct dive
 
 	for (i = 0; i < pi->nr_cylinders; i++) {
 		if (seen[i] >= 0) {
-			const cylinder_t *cyl = dive->cylinders.cylinders + i;
+			const cylinder_t *cyl = get_cylinder(dive, i);
 
 			add_plot_pressure(pi, first[i], i, cyl->start);
 			add_plot_pressure(pi, last[i], i, cyl->end);
@@ -1442,7 +1442,7 @@ static void plot_string(struct plot_info *pi, int idx, struct membuffer *b)
 		int mbar = get_plot_pressure(pi, idx, cyl);
 		if (!mbar)
 			continue;
-		struct gasmix mix = displayed_dive.cylinders.cylinders[cyl].gasmix;
+		struct gasmix mix = get_cylinder(&displayed_dive, cyl)->gasmix;
 		pressurevalue = get_pressure_units(mbar, &pressure_unit);
 		put_format_loc(b, translate("gettextFromC", "P: %d%s (%s)\n"), pressurevalue, pressure_unit, gasname(mix));
 	}
@@ -1706,7 +1706,7 @@ void compare_samples(struct plot_info *pi, int idx1, int idx2, char *buf, int bu
 		pressurevalue = get_pressure_units(bar_used, &pressure_unit);
 		memcpy(buf2, buf, bufsize);
 		snprintf_loc(buf, bufsize, translate("gettextFromC", "%s ΔP:%d%s"), buf2, pressurevalue, pressure_unit);
-		cylinder_t *cyl = displayed_dive.cylinders.cylinders + 0;
+		cylinder_t *cyl = get_cylinder(&displayed_dive, 0);
 		/* if we didn't cross a tank change and know the cylidner size as well, show SAC rate */
 		if (!crossed_tankchange && cyl->type.size.mliter) {
 			double volume_value;
diff --git a/core/qthelper.cpp b/core/qthelper.cpp
index b8afd8267..6d33be383 100644
--- a/core/qthelper.cpp
+++ b/core/qthelper.cpp
@@ -391,7 +391,7 @@ QVector<QPair<QString, int>> selectedDivesGasUsed()
 		volume_t *diveGases = get_gas_used(d);
 		for (j = 0; j < d->cylinders.nr; j++) {
 			if (diveGases[j].mliter) {
-				QString gasName = gasname(d->cylinders.cylinders[j].gasmix);
+				QString gasName = gasname(get_cylinder(d, j)->gasmix);
 				gasUsed[gasName] += diveGases[j].mliter;
 			}
 		}
@@ -1186,7 +1186,7 @@ QString get_gas_string(struct gasmix gas)
 QString get_divepoint_gas_string(struct dive *d, const divedatapoint &p)
 {
 	int idx = p.cylinderid;
-	return get_gas_string(d->cylinders.cylinders[idx].gasmix);
+	return get_gas_string(get_cylinder(d, idx)->gasmix);
 }
 
 QString get_taglist_string(struct tag_entry *tag_list)
diff --git a/core/save-git.c b/core/save-git.c
index 662891153..9e14784fe 100644
--- a/core/save-git.c
+++ b/core/save-git.c
@@ -138,7 +138,7 @@ static void save_cylinder_info(struct membuffer *b, struct dive *dive)
 
 	nr = nr_cylinders(dive);
 	for (i = 0; i < nr; i++) {
-		cylinder_t *cylinder = dive->cylinders.cylinders + i;
+		cylinder_t *cylinder = get_cylinder(dive, i);
 		int volume = cylinder->type.size.mliter;
 		const char *description = cylinder->type.description;
 		int use = cylinder->cylinder_use;
diff --git a/core/save-html.c b/core/save-html.c
index 380f2fa8e..4c9b428cb 100644
--- a/core/save-html.c
+++ b/core/save-html.c
@@ -132,7 +132,7 @@ static void put_cylinder_HTML(struct membuffer *b, struct dive *dive)
 		put_string(b, separator);
 
 	for (i = 0; i < nr; i++) {
-		cylinder_t *cylinder = dive->cylinders.cylinders + i;
+		cylinder_t *cylinder = get_cylinder(dive, i);
 		put_format(b, "%s{", separator);
 		separator = ", ";
 		write_attribute(b, "Type", cylinder->type.description, ", ");
diff --git a/core/save-xml.c b/core/save-xml.c
index a7bf6b23e..f1fbdc831 100644
--- a/core/save-xml.c
+++ b/core/save-xml.c
@@ -179,7 +179,7 @@ static void save_cylinder_info(struct membuffer *b, struct dive *dive)
 	nr = nr_cylinders(dive);
 
 	for (i = 0; i < nr; i++) {
-		cylinder_t *cylinder = dive->cylinders.cylinders + i;
+		cylinder_t *cylinder = get_cylinder(dive, i);
 		int volume = cylinder->type.size.mliter;
 		const char *description = cylinder->type.description;
 		int use = cylinder->cylinder_use;
diff --git a/core/statistics.c b/core/statistics.c
index fa7985c90..7adffa2f0 100644
--- a/core/statistics.c
+++ b/core/statistics.c
@@ -334,7 +334,7 @@ bool is_cylinder_used(const struct dive *dive, int idx)
 	if (idx < 0 || idx >= dive->cylinders.nr)
 		return false;
 
-	cyl = &dive->cylinders.cylinders[idx];
+	cyl = get_cylinder(dive, idx);
 	if ((cyl->start.mbar - cyl->end.mbar) > SOME_GAS)
 		return true;
 
@@ -369,7 +369,7 @@ volume_t *get_gas_used(struct dive *dive)
 
 	volume_t *gases = malloc(dive->cylinders.nr * sizeof(volume_t));
 	for (idx = 0; idx < dive->cylinders.nr; idx++) {
-		cylinder_t *cyl = &dive->cylinders.cylinders[idx];
+		cylinder_t *cyl = get_cylinder(dive, idx);
 		pressure_t start, end;
 
 		start = cyl->start.mbar ? cyl->start : cyl->sample_start;
@@ -408,7 +408,7 @@ void selected_dives_gas_parts(volume_t *o2_tot, volume_t *he_tot)
 		for (j = 0; j < d->cylinders.nr; j++) {
 			if (diveGases[j].mliter) {
 				volume_t o2 = {}, he = {};
-				get_gas_parts(d->cylinders.cylinders[j].gasmix, diveGases[j], O2_IN_AIR, &o2, &he);
+				get_gas_parts(get_cylinder(d, j)->gasmix, diveGases[j], O2_IN_AIR, &o2, &he);
 				o2_tot->mliter += o2.mliter;
 				he_tot->mliter += he.mliter;
 			}
diff --git a/core/subsurface-qt/DiveObjectHelper.cpp b/core/subsurface-qt/DiveObjectHelper.cpp
index 8e289d6e1..606614b05 100644
--- a/core/subsurface-qt/DiveObjectHelper.cpp
+++ b/core/subsurface-qt/DiveObjectHelper.cpp
@@ -32,7 +32,7 @@ static QString getFormattedWeight(const struct dive *dive, int idx)
 
 static QString getFormattedCylinder(const struct dive *dive, int idx)
 {
-	const cylinder_t *cyl = &dive->cylinders.cylinders[idx];
+	const cylinder_t *cyl = get_cylinder(dive, idx);
 	const char *desc = cyl->type.description;
 	if (!desc && idx > 0)
 		return QString();
@@ -46,7 +46,7 @@ static QString getFormattedCylinder(const struct dive *dive, int idx)
 
 static QString getPressures(const struct dive *dive, int i, enum returnPressureSelector ret)
 {
-	const cylinder_t *cyl = &dive->cylinders.cylinders[i];
+	const cylinder_t *cyl = get_cylinder(dive, i);
 	QString fmt;
 	if (ret == START_PRESSURE) {
 		if (cyl->start.mbar)
@@ -104,10 +104,10 @@ static QString formatGas(const dive *d)
 	for (int i = 0; i < d->cylinders.nr; i++) {
 		if (!is_cylinder_used(d, i))
 			continue;
-		gas = d->cylinders.cylinders[i].type.description;
+		gas = get_cylinder(d, i)->type.description;
 		if (!gas.isEmpty())
 			gas += QChar(' ');
-		gas += gasname(d->cylinders.cylinders[i].gasmix);
+		gas += gasname(get_cylinder(d, i)->gasmix);
 		// if has a description and if such gas is not already present
 		if (!gas.isEmpty() && gases.indexOf(gas) == -1) {
 			if (!gases.isEmpty())
@@ -167,8 +167,8 @@ static QVector<CylinderObjectHelper> makeCylinderObjects(const dive *d)
 	QVector<CylinderObjectHelper> res;
 	for (int i = 0; i < d->cylinders.nr; i++) {
 		//Don't add blank cylinders, only those that have been defined.
-		if (d->cylinders.cylinders[i].type.description)
-			res.append(CylinderObjectHelper(&d->cylinders.cylinders[i])); // no emplace for QVector. :(
+		if (get_cylinder(d, i)->type.description)
+			res.append(CylinderObjectHelper(get_cylinder(d, i))); // no emplace for QVector. :(
 	}
 	return res;
 }
@@ -178,7 +178,7 @@ QStringList formatGetCylinder(const dive *d)
 	QStringList getCylinder;
 	for (int i = 0; i < d->cylinders.nr; i++) {
 		if (is_cylinder_used(d, i))
-			getCylinder << d->cylinders.cylinders[i].type.description;
+			getCylinder << get_cylinder(d, i)->type.description;
 	}
 	return getCylinder;
 }
@@ -208,7 +208,7 @@ QStringList getFirstGas(const dive *d)
 	QStringList gas;
 	for (int i = 0; i < d->cylinders.nr; i++) {
 		if (is_cylinder_used(d, i))
-			gas << get_gas_string(d->cylinders.cylinders[i].gasmix);
+			gas << get_gas_string(get_cylinder(d, i)->gasmix);
 	}
 	return gas;
 }
@@ -239,7 +239,7 @@ QStringList getFullCylinderList()
 	int i = 0;
 	for_each_dive (i, d) {
 		for (int j = 0; j < d->cylinders.nr; j++)
-			addStringToSortedList(cylinders, d->cylinders.cylinders[j].type.description);
+			addStringToSortedList(cylinders, get_cylinder(d, j)->type.description);
 	}
 
 	for (int ti = 0; ti < MAX_TANK_INFO; ti++)
diff --git a/desktop-widgets/divelogexportdialog.cpp b/desktop-widgets/divelogexportdialog.cpp
index e093819dd..cf859e2b9 100644
--- a/desktop-widgets/divelogexportdialog.cpp
+++ b/desktop-widgets/divelogexportdialog.cpp
@@ -445,7 +445,7 @@ void DiveLogExportDialog::export_TeX(const char *filename, const bool selected_o
 		put_format(&buf, "\n%% Gas use information:\n");
 		qty_cyl = 0;
 		for (i = 0; i < dive->cylinders.nr; i++){
-			const cylinder_t &cyl = dive->cylinders.cylinders[i];
+			const cylinder_t &cyl = *get_cylinder(dive, i);
 			if (is_cylinder_used(dive, i) || (prefs.display_unused_tanks && cyl.type.description)){
 				put_format(&buf, "\\def\\%scyl%cdescription{%s}\n", ssrf, 'a' + i, cyl.type.description);
 				put_format(&buf, "\\def\\%scyl%cgasname{%s}\n", ssrf, 'a' + i, gasname(cyl.gasmix));
diff --git a/desktop-widgets/simplewidgets.cpp b/desktop-widgets/simplewidgets.cpp
index c49a9886b..5edc66e80 100644
--- a/desktop-widgets/simplewidgets.cpp
+++ b/desktop-widgets/simplewidgets.cpp
@@ -512,7 +512,7 @@ void DiveComponentSelection::buttonClicked(QAbstractButton *button)
 			text << tr("Cylinders:\n");
 			for (cyl = 0; cyl < displayed_dive.cylinders.nr; cyl++) {
 				if (is_cylinder_used(&displayed_dive, cyl))
-					text << displayed_dive.cylinders.cylinders[cyl].type.description << " " << gasname(displayed_dive.cylinders.cylinders[cyl].gasmix) << "\n";
+					text << get_cylinder(&displayed_dive, cyl)->type.description << " " << gasname(get_cylinder(&displayed_dive, cyl)->gasmix) << "\n";
 			}
 		}
 		if (what->weights) {
diff --git a/desktop-widgets/tab-widgets/TabDiveInformation.cpp b/desktop-widgets/tab-widgets/TabDiveInformation.cpp
index 6fabc3bb3..928627311 100644
--- a/desktop-widgets/tab-widgets/TabDiveInformation.cpp
+++ b/desktop-widgets/tab-widgets/TabDiveInformation.cpp
@@ -66,7 +66,7 @@ void TabDiveInformation::updateProfile()
 		gaslist.append(separator); volumes.append(separator); SACs.append(separator);
 		separator = "\n";
 
-		gaslist.append(gasname(current_dive->cylinders.cylinders[i].gasmix));
+		gaslist.append(gasname(get_cylinder(current_dive, i)->gasmix));
 		if (!gases[i].mliter)
 			continue;
 		volumes.append(get_volume_string(gases[i], true));
diff --git a/desktop-widgets/tab-widgets/maintab.cpp b/desktop-widgets/tab-widgets/maintab.cpp
index 4d3d7397d..e10575942 100644
--- a/desktop-widgets/tab-widgets/maintab.cpp
+++ b/desktop-widgets/tab-widgets/maintab.cpp
@@ -656,7 +656,7 @@ bool cylinders_equal(const dive *d1, const dive *d2)
 	if (d1->cylinders.nr != d2->cylinders.nr)
 		return false;
 	for (int i = 0; i < d1->cylinders.nr; ++i) {
-		if (!same_cylinder(d1->cylinders.cylinders[i], d2->cylinders.cylinders[i]))
+		if (!same_cylinder(*get_cylinder(d1, i), *get_cylinder(d2, i)))
 			return false;
 	}
 	return true;
diff --git a/mobile-widgets/qmlmanager.cpp b/mobile-widgets/qmlmanager.cpp
index f14092fb1..c27e2ca23 100644
--- a/mobile-widgets/qmlmanager.cpp
+++ b/mobile-widgets/qmlmanager.cpp
@@ -1125,10 +1125,10 @@ void QMLManager::commitChanges(QString diveId, QString number, QString date, QSt
 			if (state != "add" && !is_cylinder_used(d, i))
 				continue;
 
-			d->cylinders.cylinders[i].start.mbar = parsePressureToMbar(startpressure[j]);
-			d->cylinders.cylinders[i].end.mbar = parsePressureToMbar(endpressure[j]);
-			if (d->cylinders.cylinders[i].end.mbar > d->cylinders.cylinders[i].start.mbar)
-				d->cylinders.cylinders[i].end.mbar = d->cylinders.cylinders[i].start.mbar;
+			get_cylinder(d, i)->start.mbar = parsePressureToMbar(startpressure[j]);
+			get_cylinder(d, i)->end.mbar = parsePressureToMbar(endpressure[j]);
+			if (get_cylinder(d, i)->end.mbar > get_cylinder(d, i)->start.mbar)
+				get_cylinder(d, i)->end.mbar = get_cylinder(d, i)->start.mbar;
 
 			j++;
 		}
@@ -1146,8 +1146,8 @@ void QMLManager::commitChanges(QString diveId, QString number, QString date, QSt
 				he >= 0 && he <= 1000 &&
 				o2 + he <= 1000) {
 				diveChanged = true;
-				d->cylinders.cylinders[i].gasmix.o2.permille = o2;
-				d->cylinders.cylinders[i].gasmix.he.permille = he;
+				get_cylinder(d, i)->gasmix.o2.permille = o2;
+				get_cylinder(d, i)->gasmix.he.permille = he;
 			}
 			j++;
 		}
@@ -1173,9 +1173,9 @@ void QMLManager::commitChanges(QString diveId, QString number, QString date, QSt
 					break;
 				}
 			}
-			d->cylinders.cylinders[j].type.description = copy_qstring(usedCylinder[k]);
-			d->cylinders.cylinders[j].type.size.mliter = size;
-			d->cylinders.cylinders[j].type.workingpressure.mbar = wp;
+			get_cylinder(d, j)->type.description = copy_qstring(usedCylinder[k]);
+			get_cylinder(d, j)->type.size.mliter = size;
+			get_cylinder(d, j)->type.workingpressure.mbar = wp;
 			k++;
 		}
 	}
@@ -1789,8 +1789,8 @@ QStringList QMLManager::cylinderInit() const
 	int i = 0;
 	for_each_dive (i, d) {
 		for (int j = 0; j < d->cylinders.nr; j++) {
-			if (!empty_string(d->cylinders.cylinders[j].type.description))
-				cylinders << d->cylinders.cylinders[j].type.description;
+			if (!empty_string(get_cylinder(d, j)->type.description))
+				cylinders << get_cylinder(d, j)->type.description;
 		}
 	}
 
diff --git a/profile-widget/diveprofileitem.cpp b/profile-widget/diveprofileitem.cpp
index 3d0ba2e7a..2d50ad222 100644
--- a/profile-widget/diveprofileitem.cpp
+++ b/profile-widget/diveprofileitem.cpp
@@ -748,7 +748,7 @@ void DiveGasPressureItem::modelDataChanged(const QModelIndex &topLeft, const QMo
 					label_y_offset = -7 * axisLog;
 				}
 				plotPressureValue(mbar, entry->sec, alignVar, value_y_offset);
-				plotGasValue(mbar, entry->sec, displayed_dive.cylinders.cylinders[cyl].gasmix, alignVar, label_y_offset);
+				plotGasValue(mbar, entry->sec, get_cylinder(&displayed_dive, cyl)->gasmix, alignVar, label_y_offset);
 				seen_cyl[cyl] = true;
 
 				/* Alternate alignment as we see cylinder use.. */
diff --git a/profile-widget/profilewidget2.cpp b/profile-widget/profilewidget2.cpp
index 01cd733be..ccbae7cc4 100644
--- a/profile-widget/profilewidget2.cpp
+++ b/profile-widget/profilewidget2.cpp
@@ -1536,7 +1536,7 @@ void ProfileWidget2::contextMenuEvent(QContextMenuEvent *event)
 				int newGasIdx = gasChangeIdx + 1;
 				const struct plot_data &newGasEntry = plotInfo.entry[newGasIdx];
 				qDebug() << "after gas change at " << newGasEntry->sec << ": sensor pressure" << newGasEntry->pressure[0] << "interpolated" << newGasEntry->pressure[1];
-				if (get_plot_sensor_pressure(&plotInfo, gasChangeIdx) == 0 || displayed_dive.cylinders.cylinders[gasChangeEntry->sensor[0]].sample_start.mbar == 0) {
+				if (get_plot_sensor_pressure(&plotInfo, gasChangeIdx) == 0 || get_cylinder(&displayed_dive, gasChangeEntry->sensor[0])->sample_start.mbar == 0) {
 					// if we have no sensorpressure or if we have no pressure from samples we can assume that
 					// we only have interpolated pressure (the pressure in the entry may be stored in the sensor
 					// pressure field if this is the first or last entry for this tank... see details in gaspressures.c
@@ -1545,7 +1545,7 @@ void ProfileWidget2::contextMenuEvent(QContextMenuEvent *event)
 					QAction *adjustOldPressure = m.addAction(tr("Adjust pressure of cyl. %1 (currently interpolated as %2)")
 										 .arg(gasChangeEntry->sensor[0] + 1).arg(get_pressure_string(pressure)));
 				}
-				if (get_plot_sensor_pressure(&plotInfo, newGasIdx) == 0 || displayed_dive.cylinders.cylinders[newGasEntry->sensor[0]].sample_start.mbar == 0) {
+				if (get_plot_sensor_pressure(&plotInfo, newGasIdx) == 0 || get_cylinder(&displayed_dive, newGasEntry->sensor[0])->sample_start.mbar == 0) {
 					// we only have interpolated press -- see commend above
 					pressure_t pressure;
 					pressure.mbar = get_plot_interpolated_pressure(&plotInfo, newGasIdx) ? : get_plot_sensor_pressure(&plotInfo, newGasIdx);
@@ -1882,7 +1882,7 @@ void ProfileWidget2::repositionDiveHandlers()
 		QLineF line(p1, p2);
 		QPointF pos = line.pointAt(0.5);
 		gases[i]->setPos(pos);
-		gases[i]->setText(get_gas_string(displayed_dive.cylinders.cylinders[datapoint.cylinderid].gasmix));
+		gases[i]->setText(get_gas_string(get_cylinder(&displayed_dive, datapoint.cylinderid)->gasmix));
 		gases[i]->setVisible(datapoint.entered &&
 				(i == 0 || gases[i]->text() != gases[i-1]->text()));
 	}
diff --git a/profile-widget/tankitem.cpp b/profile-widget/tankitem.cpp
index e3233184c..4967633ed 100644
--- a/profile-widget/tankitem.cpp
+++ b/profile-widget/tankitem.cpp
@@ -97,7 +97,7 @@ void TankItem::modelDataChanged(const QModelIndex&, const QModelIndex&)
 
 	// start with the first gasmix and at the start of the dive
 	int cyl = explicit_first_cylinder(&displayed_dive, dc);
-	struct gasmix gasmix = displayed_dive.cylinders.cylinders[cyl].gasmix;
+	struct gasmix gasmix = get_cylinder(&displayed_dive, cyl)->gasmix;
 	int startTime = 0;
 
 	// work through all the gas changes and add the rectangle for each gas while it was used
diff --git a/qt-models/cylindermodel.cpp b/qt-models/cylindermodel.cpp
index f64cc213a..22fc5ae8b 100644
--- a/qt-models/cylindermodel.cpp
+++ b/qt-models/cylindermodel.cpp
@@ -134,7 +134,7 @@ QVariant CylindersModel::data(const QModelIndex &index, int role) const
 	if (!index.isValid() || index.row() >= rows)
 		return QVariant();
 
-	const cylinder_t *cyl = &displayed_dive.cylinders.cylinders[index.row()];
+	const cylinder_t *cyl = get_cylinder(&displayed_dive, index.row());
 
 	switch (role) {
 	case Qt::BackgroundRole: {
@@ -259,7 +259,7 @@ QVariant CylindersModel::data(const QModelIndex &index, int role) const
 
 cylinder_t *CylindersModel::cylinderAt(const QModelIndex &index)
 {
-	return &displayed_dive.cylinders.cylinders[index.row()];
+	return get_cylinder(&displayed_dive, index.row());
 }
 
 // this is our magic 'pass data in' function that allows the delegate to get
@@ -449,7 +449,7 @@ static bool show_cylinder(struct dive *dive, int i)
 	if (is_cylinder_used(dive, i))
 		return true;
 
-	cylinder_t *cyl = dive->cylinders.cylinders + i;
+	cylinder_t *cyl = get_cylinder(dive, i);
 	if (cyl->start.mbar || cyl->sample_start.mbar ||
 	    cyl->end.mbar || cyl->sample_end.mbar)
 		return true;
@@ -533,10 +533,10 @@ void CylindersModel::moveAtFirst(int cylid)
 	cylinder_t temp_cyl;
 
 	beginMoveRows(QModelIndex(), cylid, cylid, QModelIndex(), 0);
-	memmove(&temp_cyl, &displayed_dive.cylinders.cylinders[cylid], sizeof(temp_cyl));
+	memmove(&temp_cyl, get_cylinder(&displayed_dive, cylid), sizeof(temp_cyl));
 	for (int i = cylid - 1; i >= 0; i--)
-		memmove(&displayed_dive.cylinders.cylinders[i + 1], &displayed_dive.cylinders.cylinders[i], sizeof(temp_cyl));
-	memmove(&displayed_dive.cylinders.cylinders[0], &temp_cyl, sizeof(temp_cyl));
+		memmove(get_cylinder(&displayed_dive, i + 1), get_cylinder(&displayed_dive, i), sizeof(temp_cyl));
+	memmove(get_cylinder(&displayed_dive, 0), &temp_cyl, sizeof(temp_cyl));
 
 	// Create a mapping of cylinder indexes:
 	// 1) Fill mapping[0]..mapping[cyl] with 0..index
@@ -558,7 +558,7 @@ void CylindersModel::updateDecoDepths(pressure_t olddecopo2)
 	pressure_t decopo2;
 	decopo2.mbar = prefs.decopo2;
 	for (int i = 0; i < displayed_dive.cylinders.nr; i++) {
-		cylinder_t *cyl = &displayed_dive.cylinders.cylinders[i];
+		cylinder_t *cyl = get_cylinder(&displayed_dive, i);
 		/* If the gas's deco MOD matches the old pO2, it will have been automatically calculated and should be updated.
 		 * If they don't match, we should leave the user entered depth as it is */
 		if (cyl->depth.mm == gas_mod(cyl->gasmix, olddecopo2, &displayed_dive, M_OR_FT(3, 10)).mm) {
@@ -578,7 +578,7 @@ bool CylindersModel::updateBestMixes()
 	// Check if any of the cylinders are best mixes, update if needed
 	bool gasUpdated = false;
 	for (int i = 0; i < displayed_dive.cylinders.nr; i++) {
-		cylinder_t *cyl = &displayed_dive.cylinders.cylinders[i];
+		cylinder_t *cyl = get_cylinder(&displayed_dive, i);
 		if (cyl->bestmix_o2) {
 			cyl->gasmix.o2 = best_o2(displayed_dive.maxdepth, &displayed_dive);
 			// fO2 + fHe must not be greater than 1
diff --git a/qt-models/diveplannermodel.cpp b/qt-models/diveplannermodel.cpp
index 8d19afcfb..dbac82681 100644
--- a/qt-models/diveplannermodel.cpp
+++ b/qt-models/diveplannermodel.cpp
@@ -268,13 +268,13 @@ QVariant DivePlannerPointsModel::data(const QModelIndex &index, int role) const
 		case GAS:
 			/* Check if we have the same gasmix two or more times
 			 * If yes return more verbose string */
-			int same_gas = same_gasmix_cylinder(&displayed_dive.cylinders.cylinders[p.cylinderid], p.cylinderid, &displayed_dive, true);
+			int same_gas = same_gasmix_cylinder(get_cylinder(&displayed_dive, p.cylinderid), p.cylinderid, &displayed_dive, true);
 			if (same_gas == -1)
-				return get_gas_string(displayed_dive.cylinders.cylinders[p.cylinderid].gasmix);
+				return get_gas_string(get_cylinder(&displayed_dive, p.cylinderid)->gasmix);
 			else
-				return get_gas_string(displayed_dive.cylinders.cylinders[p.cylinderid].gasmix) +
+				return get_gas_string(get_cylinder(&displayed_dive, p.cylinderid)->gasmix) +
 					QString(" (%1 %2 ").arg(tr("cyl.")).arg(p.cylinderid + 1) +
-						displayed_dive.cylinders.cylinders[p.cylinderid].type.description + ")";
+						get_cylinder(&displayed_dive, p.cylinderid)->type.description + ")";
 		}
 	} else if (role == Qt::DecorationRole) {
 		switch (index.column()) {
@@ -894,7 +894,7 @@ void DivePlannerPointsModel::createTemporaryPlan()
 	struct deco_state *cache = NULL;
 	struct divedatapoint *dp = NULL;
 	for (int i = 0; i < displayed_dive.cylinders.nr; i++) {
-		cylinder_t *cyl = &displayed_dive.cylinders.cylinders[i];
+		cylinder_t *cyl = get_cylinder(&displayed_dive, i);
 		if (cyl->depth.mm && cyl->cylinder_use != NOT_USED) {
 			dp = create_dp(0, cyl->depth.mm, i, 0);
 			if (diveplan.dp) {
diff --git a/qt-models/divetripmodel.cpp b/qt-models/divetripmodel.cpp
index 220d122d4..ada648762 100644
--- a/qt-models/divetripmodel.cpp
+++ b/qt-models/divetripmodel.cpp
@@ -157,7 +157,7 @@ QVariant DiveTripModelBase::diveData(const struct dive *d, int column, int role)
 		case SUIT:
 			return QString(d->suit);
 		case CYLINDER:
-			return d->cylinders.nr > 0 ? QString(d->cylinders.cylinders[0].type.description) : QString();
+			return d->cylinders.nr > 0 ? QString(get_cylinder(d, 0)->type.description) : QString();
 		case SAC:
 			return displaySac(d, prefs.units.show_units_table);
 		case OTU:
@@ -1411,7 +1411,7 @@ bool DiveTripModelList::lessThan(const QModelIndex &i1, const QModelIndex &i2) c
 		return lessThanHelper(strCmp(d1->suit, d2->suit), row_diff);
 	case CYLINDER:
 		if (d1->cylinders.nr > 0 && d2->cylinders.nr > 0)
-			return lessThanHelper(strCmp(d1->cylinders.cylinders[0].type.description, d2->cylinders.cylinders[0].type.description), row_diff);
+			return lessThanHelper(strCmp(get_cylinder(d1, 0)->type.description, get_cylinder(d2, 0)->type.description), row_diff);
 		return d1->cylinders.nr - d2->cylinders.nr < 0;
 	case GAS:
 		return lessThanHelper(nitrox_sort_value(d1) - nitrox_sort_value(d2), row_diff);
diff --git a/qt-models/models.cpp b/qt-models/models.cpp
index ab80f95f0..7be9c2440 100644
--- a/qt-models/models.cpp
+++ b/qt-models/models.cpp
@@ -27,7 +27,7 @@ static QStringList getGasList()
 {
 	QStringList list;
 	for (int i = 0; i < displayed_dive.cylinders.nr; i++) {
-		const cylinder_t *cyl = &displayed_dive.cylinders.cylinders[i];
+		const cylinder_t *cyl = get_cylinder(&displayed_dive, i);
 		/* Check if we have the same gasmix two or more times
 		 * If yes return more verbose string */
 		int same_gas = same_gasmix_cylinder(cyl, i, &displayed_dive, true);
diff --git a/smtk-import/smartrak.c b/smtk-import/smartrak.c
index 64a613fc7..5054297ab 100644
--- a/smtk-import/smartrak.c
+++ b/smtk-import/smartrak.c
@@ -507,7 +507,7 @@ static void merge_cylinder_info(cylinder_t *src, cylinder_t *dst)
 static int smtk_clean_cylinders(struct dive *d)
 {
 	int i = tanks - 1;
-	cylinder_t  *cyl, *base = &d->cylinders.cylinders[0];
+	cylinder_t  *cyl, *base = get_cylinder(d, 0);
 
 	cyl = base + tanks - 1;
 	while (cyl != base) {
@@ -1038,24 +1038,24 @@ void smartrak_import(const char *file, struct dive_table *divetable)
 		int tankidxcol = coln(TANKIDX);
 
 		for (i = 0; i < tanks; i++) {
-			if (smtkdive->cylinders.cylinders[i].start.mbar == 0)
-				smtkdive->cylinders.cylinders[i].start.mbar = lrint(strtod(col[(i * 2) + pstartcol]->bind_ptr, NULL) * 1000);
+			if (get_cylinder(smtkdive, i)->start.mbar == 0)
+				get_cylinder(smtkdive, i)->start.mbar = lrint(strtod(col[(i * 2) + pstartcol]->bind_ptr, NULL) * 1000);
 			/*
 			 * If there is a start pressure ensure that end pressure is not zero as
 			 * will be registered in DCs which only keep track of differential pressures,
 			 * and collect the data registered  by the user in mdb
 			 */
-			if (smtkdive->cylinders.cylinders[i].end.mbar == 0 && smtkdive->cylinders.cylinders[i].start.mbar != 0)
-					smtkdive->cylinders.cylinders[i].end.mbar = lrint(strtod(col[(i * 2) + 1 + pstartcol]->bind_ptr, NULL) * 1000 ? : 1000);
-			if (smtkdive->cylinders.cylinders[i].gasmix.o2.permille == 0)
-				smtkdive->cylinders.cylinders[i].gasmix.o2.permille = lrint(strtod(col[i + o2fraccol]->bind_ptr, NULL) * 10);
+			if (get_cylinder(smtkdive, i)->end.mbar == 0 && get_cylinder(smtkdive, i)->start.mbar != 0)
+					get_cylinder(smtkdive, i)->end.mbar = lrint(strtod(col[(i * 2) + 1 + pstartcol]->bind_ptr, NULL) * 1000 ? : 1000);
+			if (get_cylinder(smtkdive, i)->gasmix.o2.permille == 0)
+				get_cylinder(smtkdive, i)->gasmix.o2.permille = lrint(strtod(col[i + o2fraccol]->bind_ptr, NULL) * 10);
 			if (smtk_version == 10213) {
-				if (smtkdive->cylinders.cylinders[i].gasmix.he.permille == 0)
-					smtkdive->cylinders.cylinders[i].gasmix.he.permille = lrint(strtod(col[i + hefraccol]->bind_ptr, NULL) * 10);
+				if (get_cylinder(smtkdive, i)->gasmix.he.permille == 0)
+					get_cylinder(smtkdive, i)->gasmix.he.permille = lrint(strtod(col[i + hefraccol]->bind_ptr, NULL) * 10);
 			} else {
-				smtkdive->cylinders.cylinders[i].gasmix.he.permille = 0;
+				get_cylinder(smtkdive, i)->gasmix.he.permille = 0;
 			}
-			smtk_build_tank_info(mdb_clon, &smtkdive->cylinders.cylinders[i], col[i + tankidxcol]->bind_ptr);
+			smtk_build_tank_info(mdb_clon, get_cylinder(smtkdive, i), col[i + tankidxcol]->bind_ptr);
 		}
 		/* Check for duplicated cylinders and clean them */
 		smtk_clean_cylinders(smtkdive);